The subject invention relates to exhaust gas recirculation (EGR) within a combustion engine.
EGR systems are increasingly being utilized to improve the efficiency of engines and reduce the harmful effects of exhaust gas on the environment. As an engine burns fuel, it produces an exhaust gas which contains unburned fuel and other impurities. The exhaust gas is redirected through the engine to burn any unburned fuel. Reburning the exhaust gas before it is released reduces the harmful effects of the exhaust gas on the atmosphere and enables the vehicle to meet government emission standards.
In order to recirculate the exhaust gas, EGR systems typically include a valve and a cooler. The valve regulates the amount of exhaust gas that is introduced back into the engine. The cooler cools the exhaust gas to a specified temperature which condenses the unburned fuel.
Prior EGR system include a separate valve and cooler. A drawback to utilizing a valve and cooler as separate components is that additional tubing is necessary, reducing the amount of space in the engine compartment. Additionally, the additional tubing allows the hot fluid to lose and/or gain heat as it is transported so that there is less control of the exhaust emission.
An exhaust gas recirculation (EGR) cooling system includes a valve and a cooler. Exhaust gas from the engine is cooled and unburned gas is recycled back to the engine. Hot fluid exhaust gas from the engine enters the system on a hot side and is returned to the engine on a cold side. The cooler is divided into a shell section for a cooling fluid and a plurality of tubes for the hot fluid. The cooling fluid enters the cooler from the valve and exits the shell through an outlet nozzle. In the preferred embodiment, the tubes are such as are available under the trademark flexfin(trademark).
The valve is attached to the hot side of the cooler and is connected to a motor which controls the opening and the closing of the valve. The valve includes a cooling fluid inlet and a hot fluid inlet and has a first chamber and a second chamber.
The cooling fluid continuously flows in through the cooling fluid inlet and into the first chamber. The motor opens the valve to allow the hot fluid to flow into the valve. The subject invention allows the cooling fluid to circulate around the valve in the first chamber, reducing the amount of heat transfer from the hot fluid to the valve components, prolonging the life of the valve. The cooling fluid flows into the second chamber and continues to remove heat from the hot fluid before entering the cooler. The hot fluid continues to transfer heat to the cooling fluid in the shell as the hot fluid flows through the tubes and exits the tubes at the cold side A. As the hot fluid is cooled, the unburned gas in the hot fluid is recycled to be burned by the engine.